Cannon is important force of shock for modern times warlike. In order to put out enemy and save ourselves, we hope it can hit the target of enemy in first deliver. So the precision of the cannon is concerned important by the national defense project at present. In this paper, we will introduce the method of measuring about artillery static directional precision, choosing laser collimation photo-electricity theodolite, designing the accessories of measuring and building an intact testing system. Using this system we can measure the straight angle and height angle of the artillery and work out the actual error. On this basement, we will analysis this measurement’s precision, draw out the bend line of precision. The result of measuring indicated that this system’s measuring precision has reached 0.06 mil.